1. Field of the Invention
The invention relates to antifuse devices and, more particularly, to recessed gate dielectric antifuse devices and methods of making the same.
2. State of the Art
Antifuse devices are commonly used to permanently program integrated circuit (IC) devices and other electrical components. Semiconductor integrated circuit devices such as flash memory, erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), dynamic random access memory (DRAM), static random access memory (SRAM), and other random access memory devices typically employ the use of antifuses to program the memory or to provide access to redundant circuitry in the memory devices. For example, memory devices and other integrated circuit devices frequently include redundant circuitry linked to operational circuitry by one or more antifuse devices. In those instances where the operational circuitry fails or is defective, one or more antifuses may be programmed to bypass the defective circuitry or to utilize available redundant circuitry in place of the defective circuitry. The use of antifuses to program conventional integrated circuit devices and to select circuitry to be used on an integrated circuit device is well known.
Gate-oxide antifuses are typically formed from conventional planar access devices (PAD) such as Metal Oxide Semiconductor Field Effect Transistors (MOSFET). MOSFETs generally include a doped polysilicon gate, a channel conduction region, and source/drain regions formed by diffusion of dopants in silicon substrates. A voltage difference may be generated between the doped polysilicon gate and the channel conduction region or the source/drain regions of the MOSFET. The voltage difference may be used to program the antifuse device. For example, antifuses have a high resistance; when a high voltage exceeding the capacity of the antifuse is applied across the antifuse, the gate-oxide of the antifuse breaks down, creating an electrically conductive path through the antifuse. The breakdown of an antifuse may include a soft breakdown, where the antifuse has a high fuse resistance, or a hard breakdown, where the antifuse has a low fuse resistance.
In an attempt to improve antifuse devices and the use of antifuses with integrated circuit devices, new antifuse structures are being developed. For example, antifuses formed from recessed access devices (RAD), as opposed to the traditional planar access devices (PAD), are being used with high-density memory cells. Recessed access device antifuses are described in U.S. patent application Ser. No. 10/933,161, now U.S. Pat. No. 7,795,094, issued Sep. 14, 2010, entitled “RECESSED GATE DIELECTRIC ANTIFUSE,” and published as US 2006/0046354, the disclosure of which is incorporated herein by reference in its entirety. The use of recessed access devices as antifuses allows the formation of smaller antifuses with integrated circuits and semiconductor devices. This is especially desirable, as the design of integrated circuit devices require smaller feature sizes and increased circuit densities.
Although some strides have been made to improve antifuse technology for use with new integrated circuit devices, further enhancements in antifuse technology are desired. In particular, as higher-density integrated circuit devices are developed, smaller antifuse devices are required. Improved reliability in antifuse devices is also desirable. The ability to control the initial breakdown point of an antifuse device is also desirable.